\begin{figure}[H]
\centering
\begin{subfigure}[b]{.3\textwidth}
\centering
\figscale{
  \begin{tikzpicture}[%
    >=stealth,
    shorten >=1pt,
    node distance=2cm,
    on grid,
    auto,
    state/.append style={minimum size=2em},
    thick,
    scale=0.3
  ]
    \node[state, rectangle, align=center] (N1) {$A$\\$EX(\$B)$};
    \node[state] (N2) [below left of=N1] {$B$};
    \node[state] (N3) [below right of=N1] {$C$};
  \end{tikzpicture}
}
\caption{Preuve complète}
\label{fig:PreuveAffichageDot1}
\end{subfigure}
\begin{subfigure}[b]{.3\textwidth}
\centering
\figscale{
  \begin{tikzpicture}[%
    >=stealth,
    shorten >=1pt,
    node distance=2cm,
    on grid,
    auto,
    state/.append style={minimum size=2em},
    thick,
    scale=0.3
  ]
    \node[state, rectangle, align=center] (N1) {$A$\\$EX(\$B)$};
    \node[state] (N2) [below left of=N1] {$B$};
    \node[state] (N3) [below right of=N1] {$C$};

    \path[->]
              (N1) edge node [above left] {$\$B$} (N2);
  \end{tikzpicture}
}
\caption{Sous-preuves}
\label{fig:PreuveAffichageDot2}
\end{subfigure}
\begin{subfigure}[b]{.3\textwidth}
\centering
\figscale{
  \begin{tikzpicture}[%
    >=stealth,
    shorten >=1pt,
    node distance=2cm,
    on grid,
    auto,
    state/.append style={minimum size=2em},
    thick,
    scale=0.3
  ]
    \node[state, rectangle, align=center] (N1) {$A$\\$EX(\$B)$};
    \node[state] (N2) [below left of=N1] {$B$};
    \node[state] (N3) [below right of=N1] {$C$};

    \path[->]
              (N1) edge node [above left] {$\$B$} (N2)
              (N1) edge node {} (N3);
  \end{tikzpicture}
}
\caption{Flèches manquantes}
\label{fig:PreuveAffichageDot3}
\end{subfigure}
\caption{Affichage de la preuve pour $EX(\$B)$}
\end{figure}